This invention relates to optical systems in general and more particularly to an improved inexpensive laser beam expander.
Laser beam expanders are required for various purposes. They are used in laboratory work, for example, to expand a two millimeter beam to one inch, and are also used in connection with high powered lasers utilized in defense work. In laboratory work, it is not uncommon to use lenses to obtain the necessary expansion. The primary disadvantage of such an expander is that the lenses must be designed for certain wave lengths and cannot be used at all for infra red. Lenses cannot be used with high power lasers because of heat problems. Thus, it has been conventional when expanding high power laser beams to use cooled, confocal parabolas or some other mirror arrangement where at least one mirror is aspheric. Using aspheric mirrors causes a number of problems. Where no obscuration is allowed, off axis sections of the aspheric surfaces must be used. These become very expensive, particularly in large sizes. Furthermore, low scatter aspheric surfaces are difficult to make. Thus, scattering of light and personnel danger become a serious problem.
It can thus be seen that there is a need for an inexpensive laser beam expander which can be used at all wave lengths, both with low power and high power lasers, and which is less subject to scattering than the expanders now in use.